1. Field of the Invention
The present invention relates to a data recording medium in which data is written and read on a sector by sector basis, a format for the data recording medium, and a data recording and reproducing device for writing and reading data, using the data recording medium.
2. Description of the Related Art
A data recording medium such as an optical disk has optically detectable guide tracks in a concentric shape or a spiral shape. In the guide tracks, a plurality of tracks are formed. Each track is divided into a plurality of sectors working as a unit for writing data. Furthermore, each sector is composed of a header field in which address data is written and a data field in which data is written.
A number of tracks formed on the data recording medium are classified into a data zone and a control zone in accordance with the contents to be written in the data field. In the data zone, user data is written, and in the control zone, control data for a disk drive device is written. Various physical formats are used for the data zone. For example, ECMA/TC31/92/100 defines a Zoned Constant Angular Velocity (ZCAV) format in which the data zone is divided into a plurality of bands (zones). ECMA/TC31/92/100 also describes a partially embossed ROM disk having a rewritable area and a read-only area in the data zone.
FIG. 6 is a diagram showing a zone structure of the data recording medium, described in the ECMA/TC31/92/100. As shown in this figure, the data recording medium has a control zone including 375 control sectors and a data zone including 10 bands. The number of sectors in each band increases toward the outer periphery of the medium, irrespective of whether the band is a rewritable area or a read-only area. Since a disk motor is controlled so as to rotate an optical disk at a constant speed, the band on the outer track side has a linear velocity higher than that of the band on the inner track side. Thus, in the data recording medium according to the ZCAV format, data is written using a write power having a pulse width gradually shortened and an output gradually increased with a plurality of bands as per unit from the inner track to the outer track. More specifically, Band 0 to Band 3 are represented using write power at Band 0 and write pulse width at Band 0; Band 4 to Band 8 are represented using write power at Band 4 and write pulse width at Band 4.
FIG. 7 is a diagram of a data structure schematically showing the structure of control data to be written in common throughout the control sectors. The control data is written for securing the inter-changeability of the optical disk which is a removable medium. The control data is composed of media characterization data, recording control data, and system data.
Each set of data includes the following parameters: The media characterization data includes parameters regarding an identifier (ID) showing a track format, i.e., the ZCAV format in this example, a modulation code ID, an error correction code ID, and a physical format such as a media type for identifying whether the data recording medium is a rewritable disk, a read-only disk, or a partially embossed ROM disk. The recording control data includes parameters regarding control conditions, such as laser wavelength, disk rotation frequency, maximum read power, and write power and write pulse width with a plurality of bands as one unit. The system data includes parameters regarding area management, such as the number of bands, the number of revolutions per data band, a type ID for identifying whether each band in a partially embossed ROM disk is a rewritable area or a read-only area.
However, the ZCAV format has the following problems:
(1) In general, the sensitivity of a recording material depends on the linear velocity; therefore, as described in the ECMA/TC31/92/100, the capacity of the recording medium must be limited. More specifically, the area of the recording medium partitioned by the innermost periphery of the data zone has a radius of, for example, 24 mm. This radius amounts to about 60% of the radius of the recording medium, i.e., 40 mm. Thus, the capacity of the recording medium is limited although a head is more accessible to the inner track side. PA1 (2) According to the ZCAV format, the number of rotations of a disk motor is controlled to be a predetermined value, so that the data transfer rate is different between the inner track band and the outer track band. In a conventional medium in which only code data is written, the access speed is important for reading the code data, so that the change in the data transfer rate has not caused critical problems. On the other hand, in the future multimedia application, real-time data such as video data and audio data, which are desired to be read at a predetermined speed, is written on the recording medium together with the code data. For this reason, it is required that the data transfer rate is kept at a predetermined value in the zones in which the real-time data is written. However, when a zoned constant linear velocity (ZCLV) format is employed while keeping the data transfer rate at a predetermined value, it takes a long time to read the code data. PA1 (3) Since data in the read-only area is written by cutting with a short wavelength laser having high precision during the production of a disk, data can be written with pits shorter than those of data in the rewritable area in which laser recording is performed by a read-only drive device. Thus, the recording density in the read-only area can be made higher than that in the rewritable area. However, in the conventional partially embossed ROM disk, a sector format in the rewritable area and a sector format in the read-only area use an identical pit length; therefore, the recording density in the read-only area is limited to the recording density of the rewritable area, making it impossible to increase the capacity of the read-only area.